Over 16 million people in the US have diabetes mellitus. Nearly 95% of these cases are of type 2 diabetes. Type 2 diabetes is responsible for the rapid increase in diabetes cases over the last few decades and is associated with insulin resistance. The body produces insulin normally (at least at first); however, the insulin signal is not properly transmitted into cells. Any mechanism by which insulin sensitivity might be enhanced has potential value in the treatment of symptoms of type 2 diabetes and other conditions related to insulin resistance (hypertension, cardiovascular disease, etc.). Chromium has been proposed to play a role in insulin signaling, and pharmacological doses of chromium have beneficial effects in diabetic patients and model animals. Understanding at a molecular level the role of chromium in insulin-signaling enhancement could lead to development of chromium-bsaed drugs for the treatment of diabetes. The importance of chromium was recently recognized by NCCAM through the funding program "Chromium as adjuvant therapy for type 2 diabetes and impaired glucose tolerance" (PA-01-114). Elucidating the role of chromium in enhancing insulin sensitivity has been hindered by a couple of experimental problems. First, the pathway by which chromium is distributed in the body has not been completely elucidated. Chromium in tissues such as liver and kidney is bound by the oligopeptide low-molecular weight chromium-binding substance (LMWCr) or chromodulin, which has been proposed to have a role in enhancing insulin signaling by interacting with insulin receptor. However, while LMWCR has been well characterized spectroscopically and magnetically, the oligopeptide has proven difficult to sequence and detect in biological matrices. The specific aims of this work are 1) to develop and utilize procedures for analyzing chromium-containing macromolecules by mass spectrometry, most notably highly acidic peptides and their Cr complexes including their fragmentation pathways, 2) to apply this knowledge to sequencing LMWCr (chromodulin) and related chromium-containing peptides, and 3) to determine the nature of the low-molar mass chromium-binding component of urine, postulated to be LMWCr. The approach will employ two advancing methodologies in mass spectrometry: electrospray ionization Fourier transform ion cyclotron resonance (ESI/FT-ICR) and matrix-assisted laser desorption ionization time-of-flight (MALDI/TOF).